Polishing of a semiconductor wafer (which will be also simply referred to as a wafer hereinafter) as typified by a silicon wafer is carried out by a method for polishing both sides of the wafel at the same time or a method for polishing a single side of the wafer.
The polishing of a single side of a wafer is performed by using a polishing apparatus shown in FIG. 7 constituted of a turn table 2 having a polishing pad 12 attached thereto, a polishing agent supply mechanism 14 which supplies a polishing agent 13 onto the polishing pad 12, a polishing head 15 which holds a wafer W, and others. The wafer W is held by the polishing head 15, the polishing agent 13 is supplied onto the polishing pad 12 from the polishing agent supply mechanism 14, and the turn table 2 and the polishing head 15 are rotated respectively so that a surface of the wafer W is slid on the polishing pad 12, thereby polishing the wafer H (see, e.g., Patent Literature 1).
Further, the wafer W is often polished in multiple stages while changing a type of the polishing pad or a type of the polishing agent, and a polishing apparatus having two turn tables or three turn tables, which is called an index type, is often used.
Here, FIG. 8 shows an example of the index type polishing apparatus having three turn tables. Such an index type polishing apparatus 11 as shown in FIG. 8 has three turn tables 2, and two polishing heads 15 are assigned to each turn table. Thus, two wafers can be polished per batch, which is superior in productivity in particular.
A polishing pad used for polishing a wafer by such a polishing apparatus is subjected to a start-up operation called seasoning before use. Although a method of seasoning differs depending on a polishing pad to be used, brushing using a soft nylon brush or brushing using a ceramic or diamond dresser is generally performed. Further, Seasoning of actually polishing a wafer (a dummy wafer) which can serve as a polishing target is also performed.
The seasoning is often performed for a long time to stabilize quality of a surface of a new polishing pad immediately after replacement. In particular, the seasoning using the dummy wafer is performed for several hours depending on a type of the polishing pad in some solutions. Thus, in case of performing the seasoning in the polishing apparatus which actually carries out polishing, the polishing must be temporarily stopped during this process. Thus, productivity of wafers is greatly reduced.
Thus, to suppress a reduction in productivity of wafers caused by the seasoning, there is adopted a method of performing the seasoning alone with the use of another simple polishing apparatus (which will be referred to as an off-line set-up apparatus hereinafter) with a turn table to which a polishing pad is attached being detachable.
To perform the seasoning of a polishing pad with the use of the off-line set-up apparatus, a turn table having the polishing pad attached thereto is first disposed to the off-line set-up apparatus. Then, the seasoning of the polishing pad is carried out. When the seasoning of the polishing pad is completed, the turn table having the seasoned polishing pad attached thereto is removed from the off-line set-up apparatus. Subsequently, the turn table is disposed to the polishing apparatus which actually polishes wafers.
As the turn table, one made of stainless or ceramics is often used. In case of a turn table having a diameter of 800 mm and a thickness of 20 mm, a weight of the turn table made of stainless is approximately 80 kg, and a weight of the turn table made of ceramics is approximately 40 kg. As described above, the turn table made of stainless has the weight larger than that of the turn table made of ceramics. Furthermore, in case of the turn table made of stainless, the turn table s deformed by heat, and polishing quality is thereby affected in some cases. Thus, it is preferable to use the turn table made of ceramics.
In case of performing the seasoning of the polishing pad with the use of the off-line set-up apparatus, the turn table which is such a heavy load as described above mast be frequently attached and detached. To easily and safely attach or detach the turn table which is a heavy load described above, such a turn table transport carriage 101 which can carry such a turn table 2 as shown in FIG. 9 while holding it in a horizontal state is used. The turn table transport carriage 101 includes a turn table holding section 103 which holds the turn table 2 and an elevating mechanism which moves up and down the turn table holding section.
The turn table holding section 103 has turn table fall prevention mechanisms 109 which are configured to prevent the held turn table 2 from falling and hold and lock the turn table 2 in the horizontal state. Rollers 110 or free bearings are installed on a surface of the turn table holding section 103 which is in contact with the turn table 2 so that the turn table 2 which is a heavy load can be readily slid.
As the elevating mechanism, a hydraulic mechanism or a mechanism using a chain or a ball screw is adopted.
Here, a general procedure of removing the turn table 2 from the polishing apparatus and moving it onto the turn table transport carriage 101 will now be described.
The turn table transport carriage 101 is arranged in front of the turn table 2, which is installed in the polishing apparatus, to be removed.
A door of the polishing apparatus is opened, and a height of the turn table holding section 103 of the turn table transport carriage 101 is adjusted to a position which is equal to or slightly lower than a height of the turn table 2. At this time, a distance between the turn table 2 and the turn table transport carriage 101 may be large depending on positions of the turn table 2 and the turn table transport carriage 101. In such a case, a guide plate is installed between the turn table 2 and the turn table transport carriage 101.
In general, the turn table 2 is fixed at a predetermined position in the polishing apparatus by a mechanical locking mechanism which prevents protrusion due to rotation at the time of e.g., polishing a wafer and vacuum suction. To remove the turn table 2 from the polishing apparatus, the mechanical locking mechanism first removed. Moreover, the vacuum suction is stopped. At this time, when the turn table 2 is lifted up by using a line of the vacuum suction to supply air, the turn table 2 can be easily moved. Additionally, the turn table 2 may be removed from the polishing apparatus while supplying water so that the turn table 2 can readily slide.
Since the rollers 110 or the free bearings are provided to the turn table holding section 103 of the turn table transport carriage 101, the turn table 2 can be safely slid. The turn table is slid to a predetermined position on the turn table holding section 103, and the turn table is held by the turn table holding section 103. Further, the turn table 2 is fixed by the turn table fall prevention mechanisms 109 and carried.
At the time of disposing to the polishing apparatus the turn table subjected to the seasoning of the polishing pad attached to the turn table by the off-line set-up apparatus, the turn table is slid into the polishing apparatus from the turn table transport carriage in the order opposite to that of removing the turn table from the polishing apparatus except that the turn table holding section of the turn table transport carriage is adjusted to the height equal to or slightly higher than the height of the turn table receiver in the polishing apparatus, thereby enabling disposing.
However, when the polishing apparatus increases in size, a diameter of the turn table to be used also increases, and hence a passage along which the turn table is carried by the turn table transport carriage must be also widened. Furthermore, a wider space is required for attachment and detachment of the turn table, and hence there is a problem that a space efficiency around the polishing apparatus becomes poorer.
In particular, in case of such an index type polishing apparatus as shown in FIG. 8, since the turn table is detached and attached from three directions, the space efficiency around the polishing apparatus is greatly lowered.
Thus, the space efficiency is improved by laying out the space for attachment and detachment of the turn table so that it is shared by polishing apparatuses adjacent to each other.
Moreover, the turn table transport carriage 101 shown in FIG. 9 is a longitudinal attachment/detachment type by which the turn table 2 is accessed from the front side and the turn table 2 is attached or detached, but a turn table transport carriage which attaches or detaches the turn table from a side surface of the turn table transport carriage 101 is sometimes used. FIG. 10 shows how the turn table is disposed to the polishing apparatus 11 by the longitudinal attachment/detachment type turn table transport carriage 101 and a lateral attachment/detachment type turn table transport carriage 101a. 
A power supply wiring line and water supply and drainage pipings (not shown) are provided around the polishing apparatus 11. Thus, as compared with the longitudinal attachment/detachment type turn table transport carriage 101, the lateral attachment/detachment type turn table transport carriage 101a is hard to access a side surface of the polishing apparatus 11 and has poorer workability. However, as shown in FIG. 10, in case of the lateral attachment/detachment type turn table transport carriage 101a, a space required for attaching or detaching the turn table to or from the polishing apparatus 11 can be reduced. Thus, a gap between the polishing apparatuses adjacent to each other can be narrowed, which is superior in the space efficiency.
However, even in case of such a lateral attachment/detachment type turn table transport carriage 101a as shown in FIG. 10, the turn table transport carriage 101a carries and attaches or detaches the turn table in the horizontal state. Thus, as the gap between the polishing apparatuses adjacent to each other, a space which is equal to or larger than a diameter of the turn table to be carried by the turn table transport carriage is required. Further, considering workability at the time of carrying the turn table by the turn table transport carriage or of attaching or detaching the turn table to or from the polishing apparatus, a space which is at least a diameter of the turn table plus 200 mm or more is required.
To uniform surface quality of a wafer when the wafer is polished by the polishing apparatus, it is desirable to perform the polishing in a state where the polishing pad is constantly in contact with the wafer. Thus, it is preferable for the diameter of the turn table to be larger than a diameter of the wafer which is a polishing target. Furthermore, to enhance productivity, the polishing apparatus 11 in which two polishing heads 15 are assigned to one turn table 2 as shown in FIG. 8 is often used.
In such a polishing apparatus, to simultaneously polish two wafers on one turn table, in case of polishing wafers each having a diameter of, e.g., 300 mm, a turn table having a turn table diameter of 800 mm is often used. As described above, since the space which is at least the diameter of the turn table plus approximately 200 mm is required, the gap for installing the polishing apparatuses adjacent to each other must be set to 1000 mm or more when the diameter of the turn table is 800 mm. As described above, in the polishing apparatus which polishes wafers each having a diameter of 300 mm or more, enhancing the space efficiency is difficult.
Meanwhile, as a large-diameter wafer whose wafer diameter exceeds 300 mm, a wafer having a diameter of 450 mm has been examined. As a turn table which can simultaneously polish two wafers each having a diameter of 450 mm, a turn table having a diameter of, e.g., 1200 mm can be used. A weight of the turn table having this size is approximately 90 kg when the turn table is made of ceramics. In case of the polishing apparatus in which a diameter of each turn table is 1200 mm, as a space for an attachment/detachment operation and carriage of each turn table using the conventional turn table transport carriage, 1400 mm or more is required.
As described above, in case of performing the attachment/detaching operation and the carriage of each turn table with the use of the conventional turn table transport carriage, these operations are always performed in a state where the turn table is horizontal, and hence the space efficiency is poor.
It is often the case where the polishing apparatus installed in a semiconductor factory is set in a clean room to suppress small scratches or defects caused by foreign particles, and the space efficiency at the time installing the polishing apparatus is affected by construction costs of the factory or running costs of utilities. Thus, an improvement in the space efficiency around the polishing apparatus has been demanded.